1. Field of the Invention
The present invention relates to lamps and methods for fabricating the same and, particularly, to a field emission lamp and a method for fabricating the same.
2. Discussion of Related Art
Fluorescent lamps are virtual necessities in modern daily living. A typical conventional fluorescent lamp generally includes a transparent glass tube. The transparent glass tube has a white or colored fluorescent material coated on an inner surface thereof and a certain amount of mercury vapor filled therein. In use, electrons are accelerated by an electric field and the accelerated electrons collide with the mercury vapor. This collision causes excitation of the mercury vapor and this excitation causes radiation of ultraviolet rays. The ultraviolet rays are absorbed by the fluorescent material and the fluorescent material emits visible light. Compared with the incandescent lamps, the fluorescent lamps have relatively high electrical energy utilization ratios. However, if or when the glass tube is broken, the mercury vapor may leak out therefrom and, because mercury is harmful to humans, mercury filled lamps can be considered as environmentally unsafe.
To address the above problems, a kind of fluorescent lamp without mercury vapor (i.e., field emission lamp) has been developed. A conventional field emission lamp, that is, a fluorescent lamp without the mercury vapor, generally includes a cathode and an anode. The cathode has a number of nanotubes formed on a surface thereof, and the anode has a fluorescent layer facing the nanotube layer of the cathode. In use, a strong electrical field is provided to excite the nanotubes. A certain amount of electrons are emitted and then accelerated from the nanotubes. Such collide with the fluorescent layer of the anode, and thereby, produce visible light. Therefore, the field emission lamp has relatively high efficiency and without being noxious to humans and the environment.
Conventionally, a transparent conductive layer (i.e. transparent conductive material) is disposed under the fluorescent layer of the field emission lamp. The electrical field can be formed between the transparent conductive layer and the emitters (i.e. nanotubes) of the cathode. The visible light produced by the fluorescent layer penetrates through the transparent conductive layer and is emitted from the lamp. Therefore, electrical conductivity and transparency are two essential properties of the transparent conductive layer used in the cold cathode field emission lamps. In prior art, a preferred material of the transparent conductive layer is indium tin oxide (ITO). The ITO can be evaporated and deposited by an industrialized method of magnetron sputtering. Though the method described above can be used in mass production, the costs of raw material and production are high.
What is needed, therefore, is to provide a field emission lamp and a method for fabricating the same, in which the transparent conductive layer has better conductivity and transparency, and the manufacture method thereof is simple, efficient, and low-cost.